Recently, electronic imaging apparatuses such as digital cameras, image input apparatuses (for instance, facsimiles, scanners, etc.), etc. for converting optical images to electric signals have been being widely used. In these electronic imaging apparatuses, however, foreign matter such as dust existing in light paths to the light-receiving surfaces of imaging devices such as photoelectric conversion devices (for instance, CCD), etc. is seen in the resultant images.
For instance, digital, single-lens reflex cameras with exchangeable photographing lenses have mirror boxes, into which dust, etc. are likely to enter when the photographing lenses are detached. Also, because mechanisms for controlling diaphragms of mirrors and photographing lenses work in the mirror boxes, dust is likely to be generated in the mirror boxes. In image input apparatuses such as facsimiles, scanners, etc., it is likely that foreign matter such as dust, etc. is generated while manuscripts are conveyed, or while manuscript-reading units move, and that the foreign matter is attached to the light-receiving surfaces of CCDs or platen glasses on which manuscripts are placed, etc. Thus, foreign matter attached to the surfaces of imaging devices, etc. is blown away using air-blowing means such as blowers, etc., but the blown foreign matter may remain in the equipment.
Particularly in digital cameras, optical filters for controlling space-frequency characteristics are disposed near imaging devices, and the optical filters are generally constituted by birefringent quartz plates. However, quartz having a piezoelectric function is easily charged by vibration, etc., and once charged, it is not easily deprived of electric charge. Accordingly, when foreign matter floats in cameras by vibration, airflow, etc. during camera operation, it is likely to be attached to the charged optical filters. Thus, cleaning with air-blowing means should be conducted frequently.
JP 2001-298640A proposes a digital camera containing a wiper, which cleans a light-receiving surface of CCD, a surface of a lowpass filter disposed on the side of the light-receiving surface of CCD, or a surface of the outermost optical member in a dust-proof unit sealing a light path to the light-receiving surface of CCD. JP 2002-204379A and JP 2003-319222A propose a camera comprising a sealed holder containing CCD and a lowpass filter, and having an opening covered with a dust-proof member (glass plate, etc.), and a means (piezoelectric element) for vibrating the dust-proof member. In this camera, dust is not attached to the CCD and the lowpass filter sealed in the holder, and dust attached to the dust-proof member can be removed by the vibrating means. However, the mechanical removal of dust described in JP 2001-298640A, JP 2002-204379A and JP 2003-319222A suffers such problems as high cost, weight increase in apparatuses, increased current consumption, etc.